The purpose of this study is to examine the effects of the serotonin reuptake inhibitor paroxetine in those who have had angioplasty or bypass surgery for coronary artery disease. Paroxetine is known as an antidepressant but may have other important uses as well. It is thought that paroxetine may benefit those with coronary artery disease by decreasing the excess adrenergic (adrenalin-like) stimulation of the heart. It is thought that too much adrenalin causes the heart to beat less efficiently and may make the heart have abnormal rhythms. We will measure adrenalin's effect on the heart by checking blood and urine and by checking the function of the heart during mild physical and mental stress. These tests will be repeated after the subjects have taken paroxetine and a medicine which has no effect on the body (placebo) so that we can compare the difference.